4 



SCIENCE. 



these are conceptions to which the idea of infinity not only 

 may be, but ought to be attached. That is to say, that the eter- 

 nal existence of Matter and the eternal duration of Force are 

 not only conceivable but true. Nay, it ma}- be our ignor- 

 ance alone, that makes us think we can conceive the con- 

 trary. It is possible to conceive of Space being utterly 

 devoid of Matter, only perhaps because we are accustomed 

 to see and to think of spaces which are indeed empty of 

 visible substances. We can expel also the invisible sub- 

 stances or gases of the atmosphere, and we can speak and 

 think of the result as a vacuum. But we know now that 

 when air and all other terrestrial gases are gone the lumi- 

 niferous medium remains ; and so far as we have means of 

 knowing, this medium is ubiquitous and omnipresent in 

 the whole universe of Space. In like manner we are accus- 

 tomed to see solid matter so dissipated as to be invisible, 

 intangible, and wholly imperceptible ; and therefore we 

 think we can imagine matter to be really destructible. But 

 the more we know of it the more certain we become that it 

 cannot be destroyed, and can only be redistributed. In 

 like manner, in regard to Force, we are accustomed to see 

 Matter in what is called statical equilibrium — that is to say, 

 at rest ; and so perhaps, we think, we can conceive the ces- 

 sation or extinction of Force. But here again the progress 

 of research is tending more and more to attach irrevocably 

 the idea of indestructibility — that is, of eternal existence — to 

 that which we know as Force. The truth is, that this con- 

 ception is really implicitly involved in the conception of the 

 indestructibility of Matter. For all that we know of Matter 

 is inseparably connected with the forces which it exerts, or 

 which it is capable of exerting, or which are being exerted 

 in it. The force of gravitation seems to be all-pervading, 

 to be either an inherent power or property in every kind, or 

 almost ever}' kind of Matter, or else to be the result of 

 some kind of energy which is universal and unquenchable. 

 All bodies, however passive and inert they may seem to be 

 under certain conditions, yet indicate by their very existence 

 the power of those molecular forces to which the cohesion 

 of their atoms is due. The fact is now familiar to us that 

 the most perfect stillness and apparent rest in many forms 

 of Matter is but the result of a balance or equilibrium 

 maintained between forces of the most tremendous energy, 

 which are ready to burst forth at a moment's notice, when 

 the conditions are changed under which that balance is 

 maintained. And this principle, which has become familiar 

 in the case of what are called explosive substances, because 

 of the ease and the certainty with which the balanced forces 

 can be liberated, is a principal which really prevails in the 

 composition of all material substances whatever ; the only 

 difference being that the energies by which their molecules 

 are held together are so held under conditions which are 

 more stable — conditions which it is much more more diffi- 

 cult to change — and conditions, therefore, which conceal 

 from us the universal prevalence and power of Force in the 

 constitution of the material universe. It is, therefore, dis- 

 tinctly the tendency of science more and more to impress us 

 with the idea of the unlimited duration and indestructible 

 nature both of Matter and of the energies which work in 

 and upon it. 



One of the scientific forms under which this idea is ex- 

 pressed is the Conservation of Energy. It affirms that 

 though we often see moving bodies stopped in their course, 

 and the energy with which they move apparently extin- 

 guished, no such extinction is really effected. It affirms 

 that this energy is merely transformed into other kinds of 

 motion, which may or may not be visible, but which, 

 whether visible or not, do always really survive the motion 

 which has been arrested. It affirms, in short, that Energy, 

 like Matter, cannot be destroyed or lessened in quaniity, 

 but can only be redistributed. 



As, however, the whole existing Order of Nature depends 

 • on very special distributions and concentrations of Force, 

 this doctrine affords no ground for presuming on the per- 

 manence, or even on the prolonged continuance, of that 

 order, yuite the contrary ; for another general conception 

 has been attained from science which at first sight appears 

 to be a contradiction of the doctrine of " Conservation of 

 Energy" — namely, the "Dissipation of Energy." This 

 doctrine, however, does not affirm that Energy can be dissi- 

 pated in the sense of being wholly lost or finally extin- 

 guished. It only affirms that all the existing concentrations 



! of force are being gradually exhausted, and that the forces 



! concerned in them are being diffused (generally in the form 



I of Heat) more and more equally over the infinitudes of 



I Matter and of Space. 



Closely connected with, if indeed it be not a necessary 

 part and consequence of, these conceptions of the infinity 

 of Space and time, of Matter and of Force, is the more gen- 

 eral concept of Causation. 



It is impossibe to conceive of anything happening with- 



| out a cause. Even if we could conceive the utter destruc- 

 tion or annihilation of any particular force or form of force, 

 we cannot conceive of this very destruction happening ex- 

 cept as the effect of some cause. All attempts to reduce 

 this idea of causation to other and lower terms have been 

 worse than futile. They have uniformly left out something 

 which is of the very essence of the idea. The notion of 

 "uniform antecedence" is not equivalent. " Necessary 

 antecedence " is more near the mark. These words do 

 indeed indicate the essential element in the idea with toler- 

 able clearness. But like all other simple fundamental con- 

 ceptions, the idea of Causation defies analysis. As, how- 

 evtr, we cannot dissociate the idea of Causation from the 

 idea of Force or energy, it may perhaps be said that the in- 

 destructibility or eternal duration of Force is a physical 

 doctrine which gives strength and substance to the meta- 

 physical concept of causation Science may discover, and 



i indeed has already discovered, that, as regards our applica- 

 tion of the idea of cause, and of the correlative idea of 

 effect, to particular cases of sequence, there is olten some 

 apparent confusion arising from the fact that the relative 

 positions of cause and effect may be interchangeable, so 

 that A, which at one moment appears as the cause of B, 

 becomes at another moment the censequence of B, and not 

 its cause. Thus Heat is very often the cause of visible 

 motion, and visible motion is again the cause of Heat. And 



; so of the whole cycle of physical forces, which Sir W. 

 Grove and others have proved to be " correlated " — that is, 

 to be so intimately related that each may in turn produce 

 or pass into all the others. But this does not really obscure 

 or cast any doubt upon the truth of our idea of causation. 

 On the contrary, that idea is confirmed in receiving a new 

 interpretation, and in the disclosure of physical facts in- 



i volving the same concepiion. The necessity of the con- 



j nection between an effect and its cause receives an unex- 

 pected confirmation when it comes to be regarded as simply 



j the necessary passing of an energy which is universal and 

 indestructible from one form of action into another. Heat 

 becomes the cause of Light because it is the same energy 

 working in a special medium. Conversely Light becomes 

 the cause of Heat, because again the same energy passes 

 into another medium and there produces a different effect. 

 And so all the so-called " correlated forces " may be inter- 

 changeably the cause or the consequence of each other, ac- 

 cording to the order of time in which the changes of form 



' are seen. This, however, does not confound, but only 

 illustrates the ineradicable conviction that for all such 

 changes there must be a cause. It may be perfectly tiue 

 that all these correlated forces can be ideally reduced to 

 different "forms of motion;" but motion itself is incon- 

 ceivable except as existing in Matter, and as the result of 

 some moving force. Every difference of direction in mo- 

 tion or of form in Matter implies a change, and we can con- 

 ceive no change without a cause — that is to say, apart from 

 the operation of some condition without which that change 

 would not have been. 



The same ultimate conceptions, and no other, appear to 

 constitute all the truth that is to be found in a favorite doc- 

 trine among the cultivators of physical science — the so- 

 called "Law of Continuity." This phrase is indeed often 

 used with such looseness of meaning that it is extremely 

 difficult to understand the primarv signification attached to 

 it. One common definition, or rather one common illustra- 

 tion, of this law is said to be that Nature does nothing sud- 

 denly — nothing " per saltum." Of course this can only be 

 accepted under some metaphorical or transcendental mean- 

 ing. In Nature there is such a thing as a flash of lightning, 

 and this is generally recognized as sufficiently sudden. A 

 great many other exertions of electric force are of similar 

 rapidity. The action of chemical affinity is always rapid, 

 and very often even instantaneous. Yet these are among 



■ the most common and the most powerful factors in the me- 



